Project Summary It is commonly appreciated that cortico-basal ganglia circuits are involved in the volitional control, initiation and cessation of movements. Perhaps less well appreciated is the role of the basal ganglia in learning and adaptive modification of skilled motor behaviors. An emerging view is that cortico-basal ganglia circuits play a prominent role in trial-and-error learning of skilled behaviors by helping to optimize future performances. Yet, the role of the cortico-basal ganglia circuits in optimizing the performance of naturally learned skilled behaviors is still poorly understood. To provide a better understanding of the basal ganglia's role in learning motor skills, we will apply closed-loop optogenetic methods in the study of a well delineated cortico-basal ganglia pathway in the songbird. Zebra finches learn to produce a complex courtship song during development and practice extensively to maintain expert performance of their song in adulthood. Using song-contingent (closed-loop) optogenetic inhibition and excitation this research will dissect the functional contribution of striatal circuits and their cortical and subcortical inputs during learning and maintenance of song. This research will test the function of different inputs to the zebra finch vocal striatum in learning and examine how prominent models of basal ganglia function, developed through the study of externally reinforced behaviors in the laboratory, bear on the learning of a naturally produced skilled motor behavior.